JPH10147694A - Stabilized polyacetal resin composition and its molding product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition, capable of maintaining excellent mechanical properties, self-lubricating properties, etc., essential to a resin and manifesting excellent characteristics of resistance to sodium hypochlorite solutions and useful for automotive parts, etc., by compounding a polyacetal resin with a specific inorganic oxide in a specified proportion. SOLUTION: This polyacetal resin composition is obtained by compounding (A) 100 pts.wt. polyacetal resin [e.g. a polymer prepared by randomly inserting (A2 ) an oxyalkylene unit such as oxyethylene unit or oxytetramethylene unit into a chain composed of (A1 ) oxymethylene unit at 0.05-50mol, especially 0.1-20mol insertion ratio of the component A2 based on 100mol component A1 ] with (B) 0.1-5 pts.wt. magnesium aluminum oxide represented by the formula Mg1-x Alx O1+x/2 [0.1<=(x)<=0.33]. The composition is remarkably improved in tensile elongation and weight retention ratio in tests on sodium hypochlorite solutions and capable of hardly changing the color tone and appearance of molding products but retaining the color tone and appearance essential to the resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel stabilized polyacetal resin composition having excellent long-term properties, especially excellent sodium hypochlorite solution properties.

[0002]

2. Description of the Related Art Polyacetal resins are used in automobiles, machinery, and the like because of their excellent mechanical strength, fatigue resistance, and self-lubricating properties.
Engineering resin widely used as electric and electronic parts. However, the polyacetal resin has a disadvantage that when left in a sodium hypochlorite solution such as tap water for a long time, the physical properties are degraded and the appearance is poor. When the polyacetal resin is used as an engineering resin, In particular, there is a demand for improved sodium hypochlorite solution properties.

It has been known that a small amount of hydrotalcite is added to a polyacetal resin in order to reduce molding distortion (warpage) and impart high cycle properties (Japanese Patent Application Laid-Open No. 57-192448). Gazette, JP 6
No. 0-104152), which not only has a different purpose from the present invention, but also has an extremely small blending amount, which leads to an improvement in the sodium hypochlorite solution characteristics of the polyacetal resin. is not.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyacetal resin and a molded article having an excellent sodium hypochlorite solution resistance as an engineering resin, which overcomes the above-mentioned problems of the conventional polyacetal resin. Is to do.

[0005]

Means for Solving the Problems The present inventor has made an effort to solve the above-mentioned problems and to develop a stabilizer capable of improving the sodium hypochlorite solution characteristics without impairing the preferable physical properties of the polyacetal resin. As a result of repeated studies, they have found that a polyacetal resin composition obtained by blending the compounds shown below can achieve the object, and based on this finding, have reached the present invention.

That is, the present invention is as follows. 1. A polyacetal resin composition comprising 0.1 to 5 parts by weight of a magnesium / aluminum oxide represented by the following formula (1) per 100 parts by weight of a polyacetal resin. Mg _1-x Al _x O _{1 + x / 2} (1) (where X is 0.1 ≦ X ≦ 0.33) A molded article obtained by molding the polyacetal resin composition of 1 above.

The polyacetal resin composition of the present invention obtained by mixing 0.1 to 5 parts by weight of the magnesium / aluminum oxide represented by the above formula (1) with respect to 100 parts by weight of the polyacetal resin, Unlike the resin composition of Example 1, the tensile elongation and the weight retention are remarkably improved in the 23 ° C. sodium hypochlorite solution test, and the appearance change of the test molded product is extremely small. Such an effect is an effect that appears for the first time in a limited addition amount region using the magnesium / aluminum oxide represented by the above formula (1).

Hereinafter, the present invention will be described in detail. The polyacetal resin used in the present invention may be either a polyacetal homopolymer or a polyacetal copolymer. The polyacetal homopolymer, oxymethylene units - (CH ₂ O) - is a polymer repeat consisting of,
It is obtained by homopolymerizing formaldehyde and trioxane.

On the other hand, the polyacetal copolymer is a polymer having a structure in which oxyalkylene units are randomly inserted into a chain composed of oxymethylene units.
The insertion ratio of oxyalkylene units in the polyacetal copolymer is preferably 0.05 to 50 mol, more preferably 0.1 to 20 mol, per 100 mol of oxymethylene units.
Is a mole.

Examples of the oxyalkylene unit include, for example, an oxyethylene unit, an oxypropylene unit, an oxytrimethylene unit, an oxytetramethylene unit, an oxybutylene unit and an oxyphenylethylene unit. Among these oxyalkylene units, an oxyethylene unit — [(CH ₂ ) ₂ O] — and an oxytetraethylene unit — [(CH ₂ ) ₄ O] — are preferred from the viewpoint of improving the physical properties of the polyacetal composition.

The polyacetal copolymer is obtained by copolymerizing a compound selected from formaldehyde, trioxane and polyoxymethylene with a cyclic ether. In addition, polyacetal block polymers in which 50% or more of the main chain is composed of repeating oxymethylene units — (CH ₂ O) — and other portions are composed of units other than oxymethylene are also included in the polyacetal copolymer. And

The magnesium / aluminum oxide used in the resin composition of the present invention has the following formula (1)
It is represented by Mg _1-x Al _x O _{1 + x / 2} (1) (in the formula, X is 0.1 ≦ X ≦ 0.33.) The addition amount of the magnesium aluminum oxide is a polyacetal resin. The amount is 0.1 to 5 parts by weight, preferably 0.15 to 4 parts by weight, and more preferably 0.2 to 3 parts by weight, per 100 parts by weight. If less than 0.1 parts by weight,
The effect of improving the properties of the sodium hypochlorite-resistant solution is insufficient, and if the amount exceeds 5 parts by weight, stagnant coloring occurs at the time of molding to deteriorate the color tone of the molded product and impair the appearance.

The magnesium-aluminum oxide used in the present invention may be, for example, an organic acid having 2 to 30 carbon atoms and at least one carboxyl group, such as stearic acid, linoleic acid, linolenic acid, etc.
Alcohols having one carbon atom (primary, secondary or tertiary alcohols), and / or these organic acids, alcohols, and metals selected from the group consisting of alkali metals, alkaline earth metals, and aluminum Surface treatment with a surfactant such as a metal salt may be performed.

Further, the composition of the present invention contains an antioxidant, a heat stabilizer, and an antioxidant commonly used in polyacetal resin compositions.
Plasticizers, UV absorbers, pigments, fillers, lubricants, flame retardants, reinforcing agents such as silica, carbon black, clay, glass fibers, carbon fibers, organic fibers, calcium carbonate, and other additives can be added. is there. The molded article of the present invention can be molded by ordinary injection molding. As an injection molding machine, a screw type, a plunger type and the like can be used. Preferred molding conditions are a cylinder temperature of 180 ° C to 230 ° C and a mold temperature of 0 ° C to 120 ° C. Other various conditions are determined according to the size, shape, and the like of the molded article, and molded.

The resin composition of the present invention can be widely used not only for applications requiring long-term sodium hypochlorite solution properties, but also for applications in contact with water, by utilizing its features. Examples of the water include water containing hypochlorite and chlorine as a disinfectant, water containing microorganisms and bacteria, water containing iron and heavy metals, and pure water containing nothing. For example, water meter gears, shower nozzle parts, water pump parts, mold remover nozzle parts, toiletry parts, etc. can be used widely.

[0016]

Next, the present invention will be described in more detail by way of examples. In addition, each characteristic of the composition in an Example and a comparative example was calculated | required as follows. (1) Long-Term Sodium Hypochlorite Solution Test A 23 ° C. sodium hypochlorite solution test was performed using a flask. However, the test water was a sodium hypochlorite solution (Kanto Chemical Co., Ltd., first class), a temperature control device was set, and the test was performed at 23 ° C. by immersion. The sodium hypochlorite solution was replaced every 168 hours. For evaluation, the tensile strength of the initial molded product and the molded product after immersion,
The elongation (according to ISO 527-1 and ISO 527-2), the weight retention and the degree of change in the appearance of the molded product were determined. (2) Change in appearance of molded article The appearance change of the initial molded article and the molded article after stagnation was visually observed and evaluated according to the following criteria. Criteria 基準: Almost no change in color tone is recognized by the naked eye. Δ: Clear whitening is clearly recognized by the naked eye. Or,
A pock pattern is sometimes observed on the molded product surface. X: White change is observed. Alternatively, a pock pattern is observed on the entire surface of the molded product.

[0017]

Examples 1 to 10 In the polyacetal resin shown in Table 2, magnesium aluminum oxide (manufactured by Kyowa Chemical Industry Co., Ltd.) shown in Table 2 and triethylene glycol-bis [3- (3 -T-butyl-5-
Methyl-4-hydroxyphenyl) propionate] was melt-kneaded to obtain pellets of the polyacetal resin composition. Using the pellets as a raw material, a tensile molded product (IS
O 3167). In addition, magnesium
The aluminum oxide shown in Table 1 was used. Table 3 shows the results of the long-term sodium hypochlorite solution test of the tensile molded product of the obtained polyacetal resin.

[0018]

Comparative Example 1 A tensile molded product was prepared and evaluated in the same manner as in Example 1 except that magnesium / aluminum oxide was not used. The results of the long-term sodium hypochlorite solution test are shown in Table 3. As is clear from the table, sufficient results were not obtained unless magnesium and aluminum oxides were blended.

[0019]

Comparative Example 2 A tensile molded product was prepared and evaluated in the same manner as in Example 4 except that the amount of magnesium / aluminum oxide added was reduced. The results of the long-term sodium hypochlorite solution test are shown in Table 3. As is clear from the table, a sufficient effect was not obtained when the addition amount of magnesium / aluminum oxide was out of the range shown in claim 1.

[0020]

Comparative Example 3 A tensile molded product was prepared in the same manner as in Example 1 except that the amount of magnesium / aluminum oxide added was increased. However, the color tone of the surface of the tensile molded product was poor. In addition, the appearance is impaired and cannot be subjected to a long-term sodium hypochlorite solution test.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

[0024]

According to the present invention, the polyacetal resin composition comprises:
Since it has excellent resistance to sodium hypochlorite solution, it can be widely used as an engineering resin for applications in contact with water, and is very useful in industry.

Claims (2)

[Claims] 1. A polyacetal resin composition comprising 0.1 to 5 parts by weight of a magnesium / aluminum oxide represented by the following formula (1) per 100 parts by weight of a polyacetal resin. Mg _1-x Al _x O _{1 + x / 2} (1) (where x is 0.1 ≦ x ≦ 0.33) 2. A molded article obtained by molding the polyacetal resin composition according to claim 1.